Rookie running back Ronnie Hillman is one of a handful of backs who will need to step up in Willis McGahee’s absence. Hillman had been getting more time gradually throughout the season but could be thrust to the forefront.

Jack Dempsey/Associated Press

Rookie running back Ronnie Hillman is one of a handful of backs who will need to step up in Willis McGahee’s absence. Hillman had been getting more time gradually throughout the season but could be thrust to the forefront.

ENGLEWOOD

The lockers of the running backs who might take Willis McGahee’s spot in the Broncos lineup are lined up conveniently, four in a row.

Lance Ball. Knowshon Moreno. Jeremiah Johnson. Ronnie Hillman.

Barring an unlikely free agent signing, some combination of those four will be asked to fill in for the foreseeable future for Denver’s leading rusher, McGahee, who tore a ligament in his right knee and will be out for what’s expected to be a six-to-eight week stint.

“We’ve all got to step up and do our part,” Hillman said. “Anyone can be an option.”

Coach John Fox said McGahee’s injury, suffered in the second quarter of Denver’s 30-23 victory over San Diego on Sunday, will not require surgery and that the Broncos had no immediate plans to put the 10th-year veteran on injured reserve. Asked about reports that McGahee also had fractured his leg, Fox said, “I don’t want to get into too much of the exacts, other than he will not be on IR.”

By not putting him on injured reserve, the Broncos, at 7-3 and with a three-game lead in the AFC West, could be thinking about a playoff-time return for their leading rusher, who has 731 yards this year and was having one of his best games of the season – 55 yards on seven carries – before the injury Sunday.

In the meantime, they must find a fill-in for McGahee, who was more reliable than explosive and spearheaded a 19th-ranked running game that’s averaging 105.3 per contest. Unlike last season, when Tim Tebow was at the helm, the running game is more complimentary than integral to an offense now run by Peyton Manning.

McGahee has built his career on adjusting to circumstances.

Back in 2003, he was finishing his college career at Miami and was considered among the very top prospects. But in the Fiesta Bowl, he tore all the ligaments in his left knee. After multiple surgeries, McGahee fell to 23rd in the draft, and even then, he sat out his first NFL season while rehabilitating the knee.

From there, he opened his career with three 1,000-yard seasons over his first four years. He went on to surpass 8,000 yards over a sturdy decade at a position where careers are often cut short. The Broncos are his third NFL team, and he is ranked first among active players with 33 100-yard games.

“His leadership. Power running. You talk about a guy who gets you the tough yards. Those are things we’re definitely going to miss,” cornerback Champ Bailey said. “But there’s a good young group behind him.”

Listed behind McGahee on last week’s depth chart was Hillman, the NFL’s youngest player at 21 years, 2 months, 5 days old. He’s a third-round draft pick out of San Diego State who ran for 1,711 yards for the Aztecs last season and slowly has been getting more playing time with the Broncos as he has picked up the intricacies of NFL pass protection.

At 5-10, 190 pounds, he looks more like a so-called “change-of-pace” back, though offensive coordinator Mike McCoy said earlier this season that the Broncos hadn’t slotted Hillman solely for that. Hillman said he could carry the ball 20 or more times if asked.

“If it happens, it happens. If not, I’ll just come in and play my role,” he said.

The next candidate is Ball, a fourth-year veteran out of Maryland, who has been a dependable backup and special teams player but still is looking for his first NFL start. Shuttling in and out with Hillman after McGahee went down against the Chargers, Ball’s biggest play of the day came when he slid over to block an oncoming Chargers linebacker, allowing Manning time to throw a 20-yard touchdown pass to Eric Decker.

Ball’s biggest rushing game came last year at Kansas City – where the Broncos play next – when he ran 30 times for 96 yards after both McGahee and Moreno went out with injuries.

“I think we all have each other’s back,” Ball said. “If Ronnie needs to come out or if he feels like I need to step in for him, I think we keep it rolling. I think that’s our mentality, is we keep the ball rolling.”

Moreno, the team’s 2009 first-round draft pick, recovered from a torn knee ligament in that game at Kansas City last year and was expected to get playing time in 2012. He hasn’t been on the active roster, however, since losing a fumble in Week 2 against Atlanta.

“That was weeks ago. I’m not thinking about that,” Moreno said. “All I’m thinking about now is now and doing the things I need to do to get on the field.”

Johnson, meanwhile, has been on Denver’s practice squad all season – a demotion of sorts after playing in eight games last season, rushing 14 times for 77 yards.

“That just gives you more of an attitude to go out there and work a little bit harder and show your teammates and the coaches that you’re willing to do anything for that team,” he said. “That’s what I’ve been trying to display to my guys, and hopefully they’ve taken to it.”

Fox didn’t rule out bringing running backs in for a look this week, though signing one would mean finding a roster spot for him. At least at this point, moving McGahee to IR didn’t sound like a possibility.

A ligament injury in his knee is expected to cost Denver running back Willis McGahee six-to-eight weeks, but the Broncos don’t plan to put him on injured reserve, perhaps holding out hope he can return for the playoffs.

Jack Dempsey/Associated Press

A ligament injury in his knee is expected to cost Denver running back Willis McGahee six-to-eight weeks, but the Broncos don’t plan to put him on injured reserve, perhaps holding out hope he can return for the playoffs.

49ers batter and bruise Bears

SAN FRANCISCO – Colin Kaepernick passed for 243 yards and two touchdowns in his first career start in place of the injured Alex Smith, and the San Francisco 49ers whipped the Chicago Bears 32-7 on Monday night in a highly touted NFC showdown that hardly lived up to the hype.

Kaepernick threw touchdown passes to Vernon Davis and Michael Crabtree, and Kendall Hunter ran for a 14-yard score as San Francisco (7-2-1) jumped out to a big lead by scoring on each of its first four possessions – with Aldon Smith wreaking havoc on the other side of the ball with five sacks.

Jason Campbell, the other quarterback in this matchup of backups for two division leaders, threw a 13-yard touchdown pass to Brandon Marshall in the third quarter but was sacked five times and threw two interceptions in his first start since October 2011 for Oakland.